The present invention relates to video signal processing apparatus and methods and, more particularly, to apparatus and methods for synchronizing a video signal.
A video processing system, such as a video decoder, may include apparatus configured to perform a 3D luminance/chrominance (Y/C) separation of an input video signal. FIG. 1 is a block diagram illustrating a conventional video signal processing apparatus 100 for performing a 3D Y/C separation. Referring to FIG. 1, the video signal processing apparatus 100 includes an analog/digital (A/D) converter 110, a Y/C separator and demodulator 120, a sync detector 130, a field/frame memory 140, and a re-sampler 150.
The A/D converter 110 converts an input analog video signal into a digital video signal. The input analog video signal may be a composite video blank sync (CVBS) signal including a front porch signal, a horizontal sync level signal, a back porch signal, and an active video signal. The sync detector 130 detects a horizontal sync position and a vertical sync position used to define horizontal and vertical scan periods from the converted digital video signal. The field/frame memory 140 stores the detected horizontal sync positions {pi} for a plurality of fields or frames. The Y/C separator and demodulator 120 performs a 3D Y/C separation according to the detected horizontal sync positions {pi} stored in the field/frame memory 140, extracts a luminance signal Y and a chrominance signal C from the converted digital video signal, interpolates the luminance signal Y and the chrominance signal C, and generates color signals, such as R, G, B color signals (R, G, B) or luminance (Y) and chrominance component (Cb, Cr) signals used by a display device (e.g., a liquid crystal display (LCD)). The color signals generated in the Y/C separator and demodulator 120 are re-sampled in the re-sampler 150 according to the horizontal sync positions {pi}. The re-sampled color signals may be used to generate a display on a display device.
When a video cassette recorder (VCR) outputs a CVBS signal, mechanical factors may cause jitter among horizontal sync positions extracted from the CVBS signal. When a TV or a digital video disk (DVD) system outputs a CVBS signal, less jitter may occur. Noise in the CVBS signal may deteriorate accuracy of the horizontal sync positions detected from the sync detector 130. Referring to FIG. 2, when the re-sampler 150 re-samples the color signals generated in the Y/C separator and demodulator 120, the screen 210 may display an unstable image due to errors in the horizontal sync positions {pi}. In particular, phase differences among the horizontal sync positions {pi} may be present, which may cause an unstable display.